Jordan said something like that: " there is no greatest of all time, there are greatest of their time"
It is reallly hard to compare player of different, and i would say even of different positions.
I like a lot of players:
Wilt: 100 points are not bad, lots of boards(that hasn't to do with the speed of the game only the third best rebounder has 7 board less then him), also quite good with assist ... and he was dominant.
Russel: the ring on his toe said it all.
the big O, Magic: probadly the best player, who archieved high level in (nearly) every basketball related skills.
Jordan: he played dominant and was a genius in marketing which briought the nba to the next level.
And now this go to non BB.